1. Field of the Invention
The present invention relates generally to turf care equipment, and more particularly, to a system which self-calibrates and which detects the occurrence of leaks in a hydraulic fluid system of a turf care machine and for providing a warning to the machine operator of such condition. Further, the present invention relates to a leak detection system which is adaptable to hydraulic fluid reservoirs of varying size and shape and which alleviates the need for fixed, tank-specific calibrations.
2. Discussion
Turf care machines are powered by a variety of means such as belts and pulleys, shafts and linkages, and the like. A common method of powering a turf care machine is to provide a source of pressurized hydraulic fluid. The pressurized hydraulic fluid can be used to power hydrostatic drive motors for propelling the turf care machine or for powering various implements such as mowers, aerators and the like. One problem with such machines is the potential for developing a leak in the hydraulic system. Should the system develop a large leak, the hydraulic fluid, under pressure, is rapidly expelled from the hydraulic system and onto the turf being treated by the machine. Often, because the machine is being operated early in the morning or late in the evening, the operator does not see the fluid spewing onto the turf until a considerable amount has leaked out, and the damage to the turf has been done. In other cases, the system develops a slow leak which leaks almost imperceptible amounts of hydraulic fluid onto the turf, but amounts sufficient to cause damage. Moreover, because the slow leak is not readily detected, fluid may be lost over several greens hence causing widespread damage. Because of the time required to grow a golf course green, sometimes several years to full maturity, and the cost associated with starting and maintaining a green, generally tens of thousands of dollars, it is vitally important to be able to detect when a machine incorporating a hydrostatic drive system has developed a leak.
U.S. Pat. No. 4,591,837 to Martinez (the Martinez system), the disclosure of which is hereby incorporated by reference, discloses a system for detecting when a hydrostatic drive system of a turf care machine has developed a leak and for providing a warning signal if such a leak occurs. The system includes a tube which communicates with and extends above the hydraulic fluid reservoir. A chamber is disposed above the tube, and there is a float disposed within the tube. At the start of operation, the machine operator fills the hydraulic fluid reservoir such that the float remains near the top of the tube. The float has a contact imbedded therein, and the tube has complementary contacts positioned such that when the float is near the top of the tube a circuit is established. During operation, expanding fluid is allowed to flow past the float and into the chamber. If a leak occurs, the fluid level within the reservoir begins to drop. If it drops a sufficient amount such that float moves away from the top of the tube, the circuit is broken and a leak is indicated.
The Martinez system suffers a number of disadvantages. First, the operator must manually drain fluid from the chamber back into the reservoir each time before using the machine. In addition, the system is only capable of accommodating a modest amount of fluid expansion. A second embodiment of the Martinez system includes a drain port for slowly allowing the fluid in the chamber to drain back into the reservoir. This relieves the operator of the task of draining the fluid back into the reservoir, however, it makes the system ineffectual for detecting small leaks. Furthermore, the Martinez system is not adapted to indicate the actual amount of hydraulic fluid within the system or the temperature of the hydraulic fluid.
Further, current leak detection systems are generally reservoir specific and require that particular, physical information, detailing the particular system on which the leak detection apparatus is installed, be hard coded into the system processor. While such calibration may be acceptable if the leak detection apparatus were installed on a limited number of hydraulic systems, such system specific calibration would be unacceptable if the size and shape of expansion tanks varied in accordance with the available space for installing the expansion tank. Thus, a particular calibration would be required for each leak detection system corresponding to a hydraulic system with an expansion tank having a unique size and shape. Furthermore, if the expansion tank incurs damage which changes the size or shape of the tank, the installation calibration fails to accurately reflect the calibrated size and shape of the expansion tank. Such a change in the size and shape requires recalibration of the physical information programmed into the processor during the original installation. Thus, a self-calibrating leak detection system would significantly improve the overall accuracy and flexibility of leak detection systems.